On April 10, 1963, the nuclear-powered attack submarine Thresher, after being overhauled, left from the Portsmouth Naval Shipyard and was undergoing deep dive tests 200 miles off the coast of New England. Suddenly something went wrong.

“We are experiencing minor difficulties, we have a positive up angle, and are attempting to blow. Will keep you informed,” a message sent by The Thresher stated at 9:13 that April day.

It was later determined the submarine likely sank due to a piping failure, loss of power and an inability to blow ballast tanks rapidly enough. The submarine was sent into a deep dive and was crushed. The Thresher sank about 200 miles southeast of Maine, in water about 8,500 feet deep. An extensive search found the ship some 8,400 feet below the surface. The dead included 16 officers, 96 enlisted men, and 17 civilians.

This tragedy led directly to significant changes in the Navy's submarine safety programs that have kept the nation's submarines safe ever since.

The Navy accelerated safety improvements and created a program called “SUBSAFE,” an extensive series of design modifications, training and other improvements.

“This has fundamentally changed the way we operate. We have never lost a submarine since and that is something we strive for. It is very important to us,” Fuller said.

This past weekend, ceremonies to remember the sailors were held in Portsmouth and Kittery.

A memorial at Portsmouth High School coordinated by U.S. Submarine Veterans Incorporated Thresher Base, a group founded in 1989 with the purpose of perpetuating the memories of the men who died onboard the ship, was held Saturday.

On Sunday morning, history was made as a 129-foot flagpole was raised on Memorial Circle on US Route 1 that now towers as a permanent memorial.

The new flagpole was manufactured by US Flag and Flagpole Supply in Wimberley, Texas. The process was made more complicated when rock was discovered underneath the site; however, engineers were able to design a foundation to hold the pole upright in time for the ceremony.

The group's larger plan for the site is still being considered by the Kittery Planning Board. The final design calls for a 25-foot circular black granite base encircling the flagpole, along with granite block signs.

The group is also working toward establishing a memorial park near the town hall. It would contain a “Thresher Circle of Honor” and courtyard, inlaid with commemorative tiles noting some of the major contributors to the project. A large granite block with a brass plaque would hold the names of the crew.

“In this close-knit community, it is clear people have come together for support. The Seacoast is a special place to be a part of,” Fuller said.